The blood pressure is usually taken while the person is seated with the arm resting on a table and slightly bent so that the arm is at the same level as the heart. The upper arm needs to be bare (with the sleeves rolled up, but not tight or uncomfortable).
Blood pressure readings are usually given as two numbers: for example, 110 over 70 (written as 110/70). The first number is called the "systolic blood pressure" reading, and it represents the maximum pressure exerted when the heart contracts. The second number (the lower number) is called the "diastolic blood pressure" reading, and it represents the pressure in the arteries when the heart is at rest.
To perform the blood pressure measurement, the blood pressure cuff is wrapped snugly around the upper arm and positioned so that the lower edge of the cuff is 1 inch above the bend of the elbow. The large artery on the inside of the elbow is located by feeling for the pulse.
The ear piece of the stethoscope is placed in the ears, and the head of the stethoscope is placed over the artery below the cuff. It should not rub the cuff or any clothing because it can make noises that will block out the pulse sounds. Correct positioning of the stethoscope is important to get an accurate recording.
The valve on the rubber inflating bulb is closed. The bulb is squeezed rapidly to inflate the cuff until the dial or column of mercury reads 30 mm Hg (millimeters of mercury) higher than the usual systolic pressure. If the usual systolic pressure is unknown, inflate to 210 mm Hg.
Now the valve is opened slightly, allowing the pressure to fall gradually (2 to 3 mm Hg per second). As the pressure falls, the level on the dial or mercury tube at which the pulsing is first heard is recorded. This is the systolic pressure.
As the air continues to be let out, the sounds will disappear. The point at which the sound disappears is recorded. This is the diastolic pressure (the lowest amount of pressure in the arteries as the heart rests).
The procedure may be repeated 2 or more times.
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